Benzene-d 6. Acetone-d 6

Transcription

1 Problem R-98B (C 12 O 2 ) 270 Mz 1 NMR Spectrum in acetone-d6 The signal at 7.3 is strongly solvent dependent ( 5.5 in CDCl 3 ) Source: I. L. Reich /19 (digitized hard copy) g O Eugenol Benzene-d 6 0 z Acetone-d

2 Problem R-98B 67.5 Mz 13 C NMR Spectra in CDCl 3 Source: Craig Puckett/Reich (digitized hard copy) /19) O Eugenol Problem R-98B FT-IR Spectrum in CCl 4 Source: I. L. Reich /19

3 Problem R-98B (C 12 O 2 ). Determine the structure (or part structure) of R-98B from the 1 NMR, 13 C NMR and IR spectra provided. (a) DBE (b) What information can you obtain from the IR spectrum? (c) Interpret the 13 C NMR spectrum. The DEPT 135 spectrum shows all C and C 3 peaks as positive, and C 2 peaks negative, the DEPT 90 is C only. Identify what kind of carbon each signal corresponds to, and write possible part structures. No Type of C (e.g. sp 3 C 2 ) and/or part structures (e.g. N-C 2 ) (d) Analyze the multiplet at 5.9 in the 270 Mz 1 NMR spectrum (shown below). Report multiplicity, coupling constants and part structure you could obtain from the signal. Draw a coupling tree

4 (e) The peaks between 6 and 7 have been provided both in acetone-d6 and in benzene-d6 solution. Do an analysis of the pattern in each solvent (give J and ), and draw the part structure identified by the pattern. Label the part structure to indicate which signals correspond to each proton. (Do not attempt to explain the solvent effect.) 0 z Acetone-d 6 Benzene-d Part structure: (f) Analyze the remainder of the signals in the 1 spectrum. Label structure fragments with J and values (g) The data provided do not allow a complete structure assignment. Draw all likely structures below. Do a chemical shift calculation for the proton you have assigned to the multiplet at 6.6 in the acetone spectrum for each possible structure, and label the structure with the calculated value (do not try to calculate all of the proton shifts). Circle the most likely structure.

5 Problem R-98B 67.5 Mz 13 C NMR Spectra in CDCl 3 Source: Craig Puckett/Reich (digitized hard copy) /19) Problem R-98B FT-IR Spectrum in CCl 4 Source: I. L. Reich /19

6 Problem R-98B (C 12 O 2 ) 270 Mz 1 NMR Spectrum in acetone-d6 The signal at 7.3 is strongly solvent dependent ( 5.5 in CDCl 3 ) Source: I. L. Reich /19 (digitized hard copy) g Benzene-d 6 0 z Acetone-d

7 2 Problem R-98B (C 12 O 2 ). Determine the structure (or part structure) of R-98B from the 1 NMR, 13 C NMR and IR spectra provided. (a) DBE 5 (b) What information can you obtain from the IR spectrum? cm -1 sharp O - perhaps intramolecularly -bonded No carbonyl cm -1 No acetylene, allene (c) Interpret the 13 C NMR spectrum. The DEPT 135 spectrum shows all C and C 3 peaks as positive, and C 2 peaks negative, the DEPT 90 is C only. Identify what kind of carbon each signal corresponds to, and write possible part structures. No Type of C (e.g. sp 3 C 2 ) and/or part structures (e.g. N-C 2 ) s s O d s d Arom, vinyl C Arom, vinyl C C or C C t d Arom, vinyl C d q Arom, vinyl C C 3 -O There are 11 C- identified from the multiplicities of the 13 C NMR spectrum. There is one missing - must be an O- (also seen in IR) 39.4 t C-C 2 -C There are different carbons - so no symmetry (d) Analyze the multiplet at 5.9 in the 270 Mz 1 NMR spectrum (shown below). Report multiplicity, coupling constants and part structure you could obtain from the signal. Draw a coupling tree. - One vinyl proton (from ) - ddt, J = 17,, 7 z this defines: J 1 (7) J 2 () J 3 (17) d ddt dd s

8 5 (e) The peaks between 6 and 7 have been provided both in acetone-d6 and in benzene-d6 solution. Do an analysis of the pattern in each solvent (give J and ), and draw the part structure identified by the pattern. Label the part structure to indicate which signals correspond to each proton. (Do not attempt to explain the solvent effect.) d, J = 8z A C Acetone-d 6 B dd, J = 8, 2 z C Benzene-d 6 0 z B dd, J = 8, 2 z A d, J = 2 z Part structure: C This must be a 1,2,4-trisubsituted benzene (O, OR) The sunstituents must be electrom donating, from B (f) Analyze the remainder of the signals in the 1 spectrum. Label structure fragments with J and values. dq, J = 17, 1.6 ddt, J =, 2.2, dt, j = 7, 1.5 z (actually ddt) 4.93 A (g) The data provided do not allow a complete structure assignment. Draw all likely structures below. Do a chemical shift calculation for the proton you have assigned to the multiplet at 6.6 in the acetone spectrum for each possible structure, and label the structure with the calculated value (do not try to calculate all of the proton shifts). Circle the most likely structure. obs 6.58 Calc: ,50 B Eugenol O B These structures fit chemical shift calculations best - hard to distinguish Note: the overlap in the middle of these signals does not result in significant second order effects because the superimposed parts are not coupled to each other (i.e. do not share energy levels) Calc 6.52 Calc 6.39 O B Other structures fit coupling, but calculated chemical shifts are off a bit more obs 6.58 Calc: Bigger error: 6.14 Calc 6.44 B O B O O MeO

9 C 12 O 2 0 Mz 1 NMR spectrum in C 6 D 6 Source: Ieva L. Reich (digitized hard copy) g O 0 z

10 C 12 O 2 0 Mz 1 NMR spectrum in CDCl 3 Source: Ieva L. Reich (digitized hard copy) g O 0 z

11 ASIS Analysis O C 6 D 6 CDC